detailview_formmixin.py

import random

from django.contrib.auth.decorators import login_required
from django.utils.decorators import method_decorator
from django.views.generic import DetailView
from django.views.generic.edit import FormMixin
from django.shortcuts import render, get_object_or_404, redirect
from django.core.urlresolvers import reverse

from products.models import Product
from items.forms import ItemForm


class ProductDetailView(DetailView, FormMixin):
    model = Product
    form_class = ItemForm

    def get_success_url(self):
        self.request.session['from_product'] = True
        return reverse('orders:register_image')

    def get_form(self, form_class=ItemForm):
        return form_class(product=self.get_object(), **self.get_form_kwargs())

    def get_context_data(self, **kwargs):
        context = super(ProductDetailView, self).get_context_data(**kwargs)
        product = self.get_object()
        related_products = sorted(
            Product.objects.related_products(product),
            key=lambda x: random.random()
        )[:3]
        context['product'] = product
        context['related_products'] = related_products
        context['item_form'] = self.get_form()
        return context

    @method_decorator(login_required)
    def post(self, request, *args, **kwargs):
        form = self.get_form()
        if form.is_valid():
            return self.form_valid(form)
        else:
            return self.form_invalid(form)

    def form_valid(self, form):
        item = self.request.user.item_set.first()
        if item:
            item.delete()
        form.save(user=self.request.user)
        return super(ProductDetailView, self).form_valid(form)

    def form_invalid(self, form):
        self.object = self.get_object()
        context = self.get_context_data()
        context['item_form'] = self.get_form()
        return self.render_to_response(context)